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|  MIL-D-19326H
3.6.9.2 Tubing flaring and bending. Aluminum alloy tubing of 5/16 and 3/8
inch (7.94 and 9.53 mm) outside diameters shall be double flared to conform with
MS33583. Aluminum alloy tubing of 1/2 inch [12.7 mm) outside diameter and all
sizes of corrosion resistant steel tubing may be single flared to conform with
MS33584. As an alternative, corrosion resistant steel tubing may be welded,
brazed or swaged using methods and quality controls that produce leakproof joints,
providing there is no undue degradation of tubing strength, corrosion resistance,
or fatigue life. Tubing systems having these permanent type joints shall be
designed for ease of fabrication, inspection and installation in the aircraft.
The system layout shall provide for rapid in-service repair and component
replacement. Tubing bends shall be uniform, without kinks, and fit the span
between fittings without tension. The minimum bend radius to tube center lines
shall be in accordance with MS33611.
3.6.9.3 Oxygen coupling sleeve. The oxygen coupling sleeve for flared tubing
shall be in accordance with Drawing 44A25450.
3.6.9.4 Tubing routing and mounting. In routing the tubing, the general
policy shall be to keep total length to a minimum consistent with Table VI. Allow
for expansion, contraction, vibration and component replacement. In all
installations of two or more converters where check valves are used, there shall
be a minimum of tubing lengths in that portion of the system between the regulator
and nearest check valve in the distribution line. To further reduce vulnerability
to gunfire, the tubing lengths, between this check valve and the converters, shall
be separated as much as possible. The separation between these tubing lengths
shall be not less than 12 inches (0.305 m). All tubing shall be mounted to
prevent vibration and chaffing. This shall be accomplished by the proper use of
rubberized or cushion clips installed at no greater than 20 inch (0.508 m)
intervals and as close to the bends as possible. Clips shall also be provided near
portable recharger connections. The tubing, where passing through or supported by
the aircraft structure, shall have adequate protection against chaffing by the use
of flexible grommets or clips. The tubing shall not strike against the aircraft
structure during vibration and shock encountered during normal use of the
aircraft.
3.6.9.5 Tubing marking.
All tubing shall be marked in accordance with
MIL-STD-1247.
3.6.10 Fittings. All fittings shall be in accordance with applicable
standards. Unless suitably protected against electrolytic corrosion, dissimilar
metals shall not be used in intimate contact with each other. Dissimilar metals
are defined in MIL-STD-889.
* 3.6.11 Torque of joints. Tightening of flared tube and pipe connections shall
be accomplished in accordance with the best commercial practice and instructions
as cited herein. Flared tube connections shall be tightened with torque wrenches,
and the torque used shall be within the limits as specified in Table VIII. The
torque limits specified in Table VIII also apply to double flared AMS 4071
aluminum tubing or MIL-T-8506 corrosion resistant annealed tubing. Straight
thread fittings which seat on an end fitting to prevent leakage shall be finger
tightened until seated. Tighten until firmly seated, and leak test. If leakage
persists, tighten slightly more until leakage is stopped. On pipe threads wrap
MIL-T-27730 antiseize tape on the threads leaving the end 1 1/2 to 2 threads
exposed, tighten the coupling nut by finger until tight, tighten by wrench another
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